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/*
* Copyright 2016 David Karnok
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package hu.akarnokd.rxjava2.subjects;
import java.util.concurrent.atomic.*;
import io.reactivex.*;
import io.reactivex.disposables.Disposable;
import io.reactivex.plugins.RxJavaPlugins;
/**
* Represents a hot Single-like source and consumer of events similar to Subjects.
*
* All methods are thread safe. Calling onSuccess multiple
* times has no effect. Calling onError multiple times relays the Throwable to
* the RxJavaPlugins' error handler.
*
* The SingleSubject doesn't store the Disposables coming through onSubscribe but
* disposes them once the other onXXX methods were called (terminal state reached).
* @param the value type received and emitted
*/
public final class SingleSubject extends Single implements SingleObserver {
final AtomicReference[]> observers;
@SuppressWarnings("rawtypes")
static final SingleDisposable[] EMPTY = new SingleDisposable[0];
@SuppressWarnings("rawtypes")
static final SingleDisposable[] TERMINATED = new SingleDisposable[0];
final AtomicBoolean once;
T value;
Throwable error;
/**
* Creates a fresh SingleSubject.
* @param the value type received and emitted
* @return the new SingleSubject instance
*/
public static SingleSubject create() {
return new SingleSubject();
}
@SuppressWarnings("unchecked")
SingleSubject() {
once = new AtomicBoolean();
observers = new AtomicReference[]>(EMPTY);
}
@Override
public void onSubscribe(Disposable d) {
if (observers.get() == TERMINATED) {
d.dispose();
}
}
@SuppressWarnings("unchecked")
@Override
public void onSuccess(T value) {
if (value == null) {
onError(new NullPointerException("Null values are not allowed in 2.x"));
return;
}
if (once.compareAndSet(false, true)) {
this.value = value;
for (SingleDisposable md : observers.getAndSet(TERMINATED)) {
md.actual.onSuccess(value);
}
}
}
@SuppressWarnings("unchecked")
@Override
public void onError(Throwable e) {
if (e == null) {
e = new NullPointerException("Null errors are not allowed in 2.x");
}
if (once.compareAndSet(false, true)) {
this.error = e;
for (SingleDisposable md : observers.getAndSet(TERMINATED)) {
md.actual.onError(e);
}
} else {
RxJavaPlugins.onError(e);
}
}
@Override
protected void subscribeActual(SingleObserver observer) {
SingleDisposable md = new SingleDisposable(observer, this);
observer.onSubscribe(md);
if (add(md)) {
if (md.isDisposed()) {
remove(md);
}
} else {
Throwable ex = error;
if (ex != null) {
observer.onError(ex);
} else {
observer.onSuccess(value);
}
}
}
boolean add(SingleDisposable inner) {
for (;;) {
SingleDisposable[] a = observers.get();
if (a == TERMINATED) {
return false;
}
int n = a.length;
@SuppressWarnings("unchecked")
SingleDisposable[] b = new SingleDisposable[n + 1];
System.arraycopy(a, 0, b, 0, n);
b[n] = inner;
if (observers.compareAndSet(a, b)) {
return true;
}
}
}
@SuppressWarnings("unchecked")
void remove(SingleDisposable inner) {
for (;;) {
SingleDisposable[] a = observers.get();
int n = a.length;
if (n == 0) {
return;
}
int j = -1;
for (int i = 0; i < n; i++) {
if (a[i] == inner) {
j = i;
break;
}
}
if (j < 0) {
return;
}
SingleDisposable[] b;
if (n == 1) {
b = EMPTY;
} else {
b = new SingleDisposable[n - 1];
System.arraycopy(a, 0, b, 0, j);
System.arraycopy(a, j + 1, b, j, n - j - 1);
}
if (observers.compareAndSet(a, b)) {
return;
}
}
}
/**
* Returns the success value if this SingleSubject was terminated with a success value.
* @return the success value or null
*/
public T getValue() {
if (observers.get() == TERMINATED) {
return value;
}
return null;
}
/**
* Returns true if this SingleSubject was terminated with a success value.
* @return true if this SingleSubject was terminated with a success value
*/
public boolean hasValue() {
return observers.get() == TERMINATED && value != null;
}
/**
* Returns the terminal error if this SingleSubject has been terminated with an error, null otherwise.
* @return the terminal error or null if not terminated or not with an error
*/
public Throwable getThrowable() {
if (observers.get() == TERMINATED) {
return error;
}
return null;
}
/**
* Returns true if this SingleSubject has been terminated with an error.
* @return true if this SingleSubject has been terminated with an error
*/
public boolean hasThrowable() {
return observers.get() == TERMINATED && error != null;
}
/**
* Returns true if this SingleSubject has observers.
* @return true if this SingleSubject has observers
*/
public boolean hasObservers() {
return observers.get().length != 0;
}
/**
* Returns the number of current observers.
* @return the number of current observers
*/
/* test */ int observerCount() {
return observers.get().length;
}
static final class SingleDisposable
extends AtomicReference> implements Disposable {
private static final long serialVersionUID = -7650903191002190468L;
final SingleObserver actual;
SingleDisposable(SingleObserver actual, SingleSubject parent) {
this.actual = actual;
lazySet(parent);
}
@Override
public void dispose() {
SingleSubject parent = getAndSet(null);
if (parent != null) {
parent.remove(this);
}
}
@Override
public boolean isDisposed() {
return get() == null;
}
}
}